在类c++中使用new声明数组

declaring an array using new in a class c++

本文关键字：new 声明 数组 c++ 在类      更新时间：2023-10-16
#include <iostream>
using namespace std;
class Point {
int x, y;
public:
Point ():x(0),y(0){};
void setX (int xx){x = xx;};
void setY (int yy){y = yy;};
int getX (){return x;};
int getY (){return y;};
};
class Polygon {
int n;
double degree;
Point* vertex;
public:
Polygon (int nn):n(nn){
degree = 360.0 / n;
//vertex = new Point [n];
};
private:
vertex = new Point [n];
};

所以我试图用new声明顶点数组，但我一直得到这个错误：数据成员初始值设定项不允许

是否考虑初始化"new"？！我试着在构造函数中做这件事，但我认为它只会在构造函数的范围内工作。

我也对此感到困惑：n应该在使用new之前初始化，所以如果我只是在构造函数之后写声明，这会解决吗？

class Point {
public:
Point ():x(0),y(0){};
void setX (int xx){x = xx;}
void setY (int yy){y = yy;}
int getX (){return x;}
int getY (){return y;}
//change access level to 'private'.
private:
int x;
int y;
};
class Polygon {
public:
Polygon (int nn):n(nn){
degree = 360.0 / n;
vertex = new Point [n];
}
// deallocate memory from heap
~Polygon () {
delete [] vertex;
}
// overload copy constructor to avoid double free 
Polygon (const Polygon& pg) : n(pg.n), degree(pg.degree) {
vertex = new Point [n];
for (int i = 0; i < n; i++) {
vertex[i] = pg.vertex[i];
}
}
// overload assignment operator to avoid memory leak
Polygon& operator=(const Polygon& pg) {
if (this != &pg) {
n = pg.n;
degree = pg.degree;
delete [] vertex;
vertex = new Point[n];
for (int i = 0; i < n; i++) {
vertex[i] = pg.vertex[i];
}
}
return *this;
}
// use pointer to change/get the value.
Point* get_vertex() {
return vertex;
}
//change access level to 'private'.
private:
int n;
double degree;
Point* vertex;
};
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